John Gamel asked:
How is caffeine extracted from whole coffee beans?
Chris - I have to say until he raised the question, I havenít even considered it but itís a very good question.
Kat - It is. I am a decaf coffee drinker. Iím caffeine-free so this actually intrigued me as well. In fact, thereís a number of different ways that people get the caffeine out of coffee. They do it on the whole beans. Itís not when you brew up the coffee and then take the caffeine out of it. You decaffeinate the beans before theyíre even roasted because that helps preserve as much flavour as possible when theyíre finally roasted and then ground up. So, thereís a number of ways you can do it. You can do it the nasty way, which is to bung a load of solvents in there. Caffeine dissolves in certain solvents, some of the ones kind of slightly related to things like dry cleaning fluid (not very nice way of treating a coffee). So people try and develop other ways of doing it with things like water. You can basically just try and wash the caffeine out by washing the beans and then filter out the the caffeine. Thereís another really clever way that people do it is by washing the coffee beans with a very, very strong solution of coffee thatís sort of saturated with all the coffee flavour molecules.
Chris Smith: But presumably decaf.
Kat - But not caffeine.
Chris Smith: Right.
Kat - So, basically itís using, I guess itís osmosis isnít it, sort of.
Chris Smith: Diffusion. Itís the diffusion gradient.
Kat - Thatís the one.
Chris Smith: If thereís no caffeine in the solution and thereís lots of caffeine in the bean thereíll be a net movement into the solution.
Kat - Exactly, the caffeine goes out the beans into this coffee-flavoured solution, but you donít lose any of the flavour from the beans because thereís already loads of these flavour molecules in the water so they donít want to move out of the beans. Thatís another way of doing it using carbon dioxide as well, high-pressure carbon dioxide which kind of forces the caffeine out without losing the flavour. So, that is apparently how they do it.